Vegetation structure and temporality influence the dominance, diversity, and composition of forest acoustic communities

Abstract

Abstract Bioacoustic methods analyze sounds to monitor wildlife in forests, providing novel perspectives to understand the relationship between forest vegetation structure and wildlife species. Bioacoustic studies differ from traditional field surveys that are often more visual and require work in the daytime. A sampling of acoustic signals is possible to explore the diurnal variation of the forest ecosystem. Normalized difference soundscape index (NDSI), acoustic diversity index (ADI), and power spectral density (PSD) were chosen as acoustic indices to quantify the dominance, diversity, and composition of the biophony of forest settings. Biophony was recorded in ten south subtropical evergreen broad-leaved forest sites in Shenzhen, China. Composition structure (species richness), horizontal structure (vegetation density and canopy cover), and vertical structure (tree height diversity and each layer height) were used to evaluate the structure of vegetation. Linear Mixed Models (LMMs) were applied to examine the effects of different vegetation structures on biophony between day and night. The relationships between various biophonic frequency bands and vegetation structural variables during day and night were estimated by redundancy analysis (RDA). Results showed that different sound frequencies and vocalization behavior of vocalizing species determine the variance between the forest sound environment during day and night. Forest canopy and understory have a significant influence on biophonic diversity and dominance separately. The vocalizing species preferences for different habitats were affected by the same vegetation structure variables across diurnal variation. Canopy cover and understory species richness had a significant positive effect on low-frequency biophony, and tree height diversity was found to have a significant positive impact on high-frequency biophony. Finally, tree height diversity was the core variable in the forest acoustic environment, and higher tree height diversity resulted in a more dominant and diverse biophony. This study shows the potential of bioacoustic methods to reveal the day-night dynamics of vocalizing species, using easily measured acoustic variables that can help with the timely evaluation of potential impacts of vegetation structure on forest animal communities.